Thanks, this was actually part b where part a was to derive the velocity transformations in the direction perpendicular to motion, which I had incorrectly found to be u'=u, but your comment made me rethink that. Thanks for the help.
Homework Statement
A rocket passes the Earth at 0.8c. As it goes by, it launches a projectile at 0.6c perpendicular to the direction of motion. What is the projectile's speed in the Earth's reference frame?
Homework Equations
[;u=\frac{u'+v}{1+u'v/{c}^{2}};]
The Attempt at a Solution
Since...